This is an application to investigate the origin of "endogenous" DNA adducts (i.e., those not derived directly from exogenous chemicals). The hypothesis to be tested is that electrophilic products of deoxyribose oxidation in DNA can react with bases to form adducts. This hypothesis is based on the applicant's observation that a product of 4'-oxidation of deoxyribose reacts with DNA to form a mutagenic guanine adduct previously thought to be derived from malondialdehyde, a product of lipid peroxidation. This proposed project will systematically explore the chemistry of DNA base adduction by several electrophilic deoxyribose oxidation products. Studies in aim 1 will examine base propenals as a source of the pyrimidopurinone of guanine, M1G. M1G adducts will be measured in DNA exposed in vitro toDNA-directed oxidant antibiotics or to peroxynitrite and iron- or copper-hydrogen peroxide mixtures. In other studies, the relative roles of lipid peroxidation aldehyde products and base propenals will be compared in oxidations with yeast, bacteria and mammalian cells. Studies in aim 2 will examine the role of phosphoglycoaldehyde residues in the formation of etheno adducts of adenine, guanine and cytidine in DNA. As in aim 1, both in vitro studies with DNA and studies with cell model systems will be used to compare phosphoglycoaldehyde and lipid peroxidation-derived aldehydes as sources of etheno adducts. Studies in aim 3 will examine products of base modification by 1,4-dioxo-2-butene and formyl phosphate from 5'-H abstraction-initiated deoxyribose oxidation in DNA. The focus of aim 4 is the biosynthesis of [U-13C]- and [U-14C]-deoxyribose-containing DNA for studies of the deoxyribose origin of adducts.